Although the variety of dyes and pigments known in the art is very wide, there is a continuing effort by synthetic dye chemists to discover new chromophoric systems for use as colorants in a broad range of applications. These applications include: textile dyes, hair dyes, paint pigments, printing inks, rubber and plastic colorants, polymer stabilizers, electrochromic and thermochromic display devices, laser dyes, electrophotographic pigments, sensitizing image, and filter dyes for photographic systems, liquid crystal display devices, optical disks, biological stains, and others.
A wide variety of dyes is employed in photographic materials. In addition to the diverse dyes used to form images in color photographic elements, spectral sensitizing dyes are used to extend the sensitivity of silver halides, which are inherently sensitive only to blue light, to other wavelengths of radiation. Among the dyes commonly employed for this purpose are the cyanines and merocyanines, which are discussed in T. H. James, ed., The Theory of the Photographic Process, 4th Ed., Macmillan, New York, 1977, Chapter 8, and in F. M. Hamer, Cyanine Dyes and Related Compounds, Wiley, New York, 1964.
Dyes are also used in color photographic materials as filters, typically located in overcoats or interlayers, to absorb incident radiation and improve image sharpness. In addition to the previously mentioned cyanines and merocyanines, various oxonol and arylidene dyes are frequently utilized for this purpose. A discussion of arylidene dyes can be found in K. Venkataraman, The Chemistry of Synthetic Dyes, Academic Press, New York, 1970, Vol. III.
Enamine structures are the tautomeric forms of imines, as shown below. ##STR3## In general, the imine is the predominant form; a stable enamine usually requires that there be no hydrogen substituent on the nitrogen atom (see J. March, Advanced Organic Chemistry, 3rd Ed., Wiley, New York, 1985, pages 69-70).
Many examples of cyanine and merocyanine dyes containing enamine substitutents are known in the art. U.S. Pat. No. 3,637,395, for example, discloses cyanine and merocyanine dyes containing cyclic enamine groups with the nitrogen at a bridgehead. Cyanine dyes containing enamines substituted with a cyclohexene ring are disclosed in U.S. Pat. No. 3,652,288, and pyrrolidinylenamine derivatives are described in U.S. Pat. No. 3,655,392. Also, U.S. Pat. No. 3,671,648 discloses tricarbocyanine dyes that contain enamine and enaminium salt groups and are useful as spectral sensitizers and filter dyes. U.S. Pat. No. 3,774,122 discloses dye lasers that contain solutions of bridged enamine cyanine dyes. Other cyanine dyes derived from enamines are described in U.S. Pat. Nos. 3,672,905, 3,786,046, and 3,915,715.
Arylidene dyes contain ethylene groups that typically are substituted at the terminal carbon atom with two strongly electron-withdrawing substituents containing multiple-bonded electronegative atoms. These substituents, which are discussed in the previously mentioned March, Advanced Organic Chemistry, pages 237-239, include cyano, acyl, aminocarbonyl, alkoxycarbonyl, and alkylsulfonyl, among others. In many arylidene dyes known in the art, both terminal substituents are cyano, as disclosed, for example, in U.S. Pat. No. 4,006,178, DE 2,246,437 (C.A. 78:159283b) and DD 222321 (C.A. 104:131452n). Other arylidene dyes containing various strongly electron-withdrawing substituents in addition to cyano on the terminal carbon atom are disclosed in U.S. Pat. No. 3,595,863, GB 2,077,751 (C.A. 96:182763p), DE 2,910,662 (C.A. 92:24254m), and DE 3,427,200 (C.A. 105:210403w). U.S. Pat. Nos. 3,597,434 and 3,879,434 disclose bis-methine dyes.
Arylidene dyes containing three strongly electron-withdrawing ethylenic substituents are disclosed in U.S. Pat. No. 4,167,490. Tricyanosubstituted methine dyes are described in JP 60/194189 (C.A. 104:150738b).
Fluorescent iminocoumarin dyes substituted on the nitrogen atom with an ethylenic moiety containing strongly electron-withdrawing groups are disclosed in DE 2,717,599 (C.A. 88:75311c) and IN 145954 (C.A. 92:148518v). Similar N-(.beta.,.beta.-dicyanovinyl) iminocoumarin dyes are disclosed in DD221,191 (C.A. 104:111374k). FR 1,549,583 (C.A. 72:22587k) describes anthraquinone dyes containing tricyanovinylamino substituents.
We have now unexpectedly found that dye compounds with new chromophoric systems can be produced from certain novel activated enamine compounds, as described herein. Variations in the substituents in these dye compounds allow modifications of their hue and absorbance over a wide range. Furthermore the incorporation of base-ionizable substituents makes them especially suitable for use as filter dyes in photographic elements.